Bright Annealing

Bright Annealed Definition

Bright annealing (BA) refers to stainless steel material is heated in closed furnace in reducing atmosphere of inert gases, common Hydrogen gas, after fast annealing, rapid cooling, stainless steel has a protective layer on the outer surface, no reflect in open air environment, this layer can resist corrosion attack. In general, material surface is more smooth and brighter.

Before Bright Annealing

The tube surface must be clean, with no foreign particles present, because any particles left on the tubing surface can cause damage during the process.

Inserted Gas

Annealing atmosphere should be free from Oxygen, isolating material, creating a vacuum condition. Inserted gas, common dry hydrogen or argon, can obtain bright result.

Annealing Temperature

Annealing temperature should be noticed depending on different stainless grades, commonly Austenitic steels annealing temperature is at least 1040 degree, soak time is not important. high temperature must be required to have brighter appearance. Heating is done as fast as possible, slow heat results in oxidation.

Some Ferritic stainless steels require lower annealing temperature, such as TP439, cannot be effectively bright annealed, Water quenching will cause scale formation.

Bright Annealing Welded Tube

Welded Tube is annealed in a vacuum controlled atmosphere to keep the surface free of oxidation and bright, in this bright annealing process, protective gas is inserted in the closed furnace, usually the gas is purified hydrogen, or mixture of hydrogen and nitrogen atmosphere from dissociated ammonia, when tube is heated up to certain specified temperature and rapid cooling, a bright and smooth protective layer is formed on the surface of tube.

Purpose & Advantages of Bright Annealed

Eliminate work hardening and obtain satisfactory metallographic structure.

Obtain a bright, non-oxidizing surface with good corrosion resistance.

The bright treatment maintains the smoothness of the rolled surface, and the bright surface can be obtained without post-processing.

No pollution problems caused by common pickling methods.